This invention relates to a sensor system for measuring the flight motions of a spinning vehicle with respect to a classical Euler angle system of coordinates that aligns itself with the plane of total angle of attack by means of a pendulum mass.
The motion of flight vehicles is usually determined from sensors such as rate gyros and accelerometers rigidly fixed in the vehicles. This has certain advantages for non-spinning vehicles such as aircraft, for which motion perturbations from a steady flight condition are desired in order to control the flight motions with respect to the vehicle axes.
For a spinning, axisymmetric body such as a ballistic reentry vehicle the use of body-fixed motion sensors has some deficiencies. The angles of attack and sideslip and the lateral rates determined from body-fixed sensors are, in general, rapidly varying quantities that oscillate at the body frequencies.
These deficiencies can be avoided by use of a sensor system that rotates in the vehicle and is inertially stabilized with respect to the lift vector or plane of total angle of attack.